In-flight refueling (or air-to-air refueling) is an important method for extending the range of both manned and unmanned aircraft traveling long distances over areas having no feasible landing or refueling points. Although in-flight refueling is a relatively common operation, especially for military aircraft, precise positioning of a second aircraft (the receiver aircraft, for example) with respect to a first aircraft (the tanker aircraft, for example) is required in order to provide a safe engagement of the first aircraft (and a refueling system carried thereby) with the second aircraft for the dispensing of fuel. The requirement of precise relative spatial positioning of two rapidly moving aircraft makes in-flight refueling a challenging operation.
One conventional system for in-flight refueling is the boom in-flight refueling system. The boom in-flight refueling system typically comprises a rigid boom carried by and lowered from a rear portion of a fuselage of a first aircraft. The aft end of the boom includes an extendable tube with a refueling nozzle attached to its aft end. The forward end of the boom is attached to the first aircraft and may be pivoted in the vertical and lateral directions. Near the aft end of the boom are airfoils, which may be controlled by an in-flight refueling system operator onboard the first aircraft. The airfoils provide maneuverability of the boom with respect to an aircraft that is to be refueled (the second aircraft) and allow the in-flight refueling operator to position the boom relative to the second aircraft, by for instance, actuating the airfoils so as to “fly” the boom to a refueling position relative to the second aircraft. First, an operator of the second aircraft must maneuver the second aircraft to within an in-flight refueling position, below and aft of the first aircraft. Upon maneuvering into the in-flight refueling position, the in-flight refueling system operator on board the tanker aircraft may control the airfoils to position the boom such that the extendable refueling nozzle of the boom may be extended to engage a refueling receptacle on the second aircraft. The in-flight refueling system operator is responsible for maintaining the position of the boom relative to the refueling receptacle as the refueling nozzle is extended towards the second aircraft. The in-flight refueling system operator, however, may have limited control of the in-flight refueling boom, due to the range of motion of the in-flight refueling boom and the airfoils attached thereto, as described below.
In conventional boom in-flight refueling systems, the airfoils are attached to an end of the boom and radially extend from the boom in a “V” configuration such that the airfoils may be configured to control the in-flight refueling boom through both a vertical range of motion (elevation, for instance) and a horizontal range of motion (azimuth, for instance). According to conventional systems, the airfoils typically rotate only about a torque tube defined by within the airfoil (wherein the torque tube may be positioned anywhere within the airfoil or along a leading edge of the airfoil, the leading edge being an edge of the airfoil nearest the tanker aircraft). As such, the airfoils of conventional boom in-flight refueling systems may have a relatively limited range of motion such that they may be ineffective in controlling the in-flight refueling boom outside of a limited elevation and azimuth range. As such, the in-flight refueling operator may not be able to adequately control to the in-flight refueling boom to engage a refueling receptacle carried by a second aircraft when the second aircraft approaches the tanker aircraft from a position outside the relatively limited range of motion of the in-flight refueling boom. This may be problematic in cases wherein, for instance, the second aircraft is a large aircraft, such as for instance a bomber aircraft or airlift aircraft having a large amount of control inertia. In such cases, it may be difficult for an operator of the second aircraft to adjust the position of the second aircraft relative to the first aircraft and the second aircraft may be forced to abort the approach to the tanker aircraft and return for another approach in an attempt to attain a position relative to the tanker aircraft wherein the limited range of motion of the in-flight refueling boom will allow it to become engaged with the refueling receptacle carried by the second aircraft. The delay incurred by having to retry a tanker approach in this manner may be detrimental to military missions having critical time constraints. In addition, the second aircraft may have very little fuel remaining upon approaching the tanker aircraft, such that it may be critical to the safety of the second aircraft and the crew aboard that the first tanker approach results in a refueling engagement with the in-flight refueling boom.
Thus, it would be advantageous to improve the range of motion of the airfoils such that the range of elevation and azimuth travel of the in-flight refueling boom (relative to the tanker aircraft) may be expanded relative to conventional boom in-flight refueling systems. This may, in turn, allow the in-flight refueling operator to have improved control over the in-flight refueling boom so as to more effectively engage a refueling receptacle carried by the second aircraft even in cases where the second aircraft approaches the tanker aircraft from a position outside the most optimal in-flight refueling position.
Therefore, there exists a need for an in-flight refueling system, boom, and method that provides for an increased range of elevation and azimuth travel for the in-flight refueling boom, relative to the tanker aircraft from which it extends during an in-flight refueling operation. Thus, there exists a need for an airfoil operably engaged with an in-flight refueling boom such that the airfoil has an expanded range of motion so as to have the capability of guiding the in-flight refueling boom through an expanded range of elevation and azimuth travel relative to conventional boom in-flight refueling systems.